1. Field of the Invention
The invention relates to a semiconductor device and fabrication method thereof, and more particularly relates to a memory device and fabrication method thereof.
2. Description of the Related Art
Integrated circuits, including dynamic random access memory (DRAM), are continuously being developed toward higher speeds and miniaturization. Additionally, it is important for memory devices to increase capacity.
FIG. 1 shows a plan view of a conventional deep trench dynamic random access memory. A plurality of oval-shaped deep trench capacitors 102, also referred to as memory elements, are crossly arranged and controlled by word lines 106 extending in a vertical direction and bit lines extending in a horizontal direction. It is noted that this figure does not show the bit lines, but shows the active areas 104 under the bit lines. Because DRAM 100 integrity and density is required to be as high as possible, the memory units and transistors are required to be as small as possible with increased speed. However, the electrode plates of the memory units have insufficient areas to store electric charges in future technology. Specifically, as memory units shrink, fabrication of the oval-shaped deep trench capacitors 102 encounter challenges during the etching process, wherein the edge length surface areas of the oval-shaped deep trench capacitors 102 are not sufficient.